Commit 8781ba0a authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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[PATCH] USB: optimise devio.c::usbdev_read 



this is a small optimisation. It is ridiculous to do a kmalloc for
18 bytes. This puts it onto the stack.

Signed-off-by: default avatarOliver Neukum <oliver@neukum.name>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 60f78052

drivers/usb/core/devio.c

+8 −13
Original line number Diff line number Diff line
@@ -134,26 +134,21 @@ static ssize_t usbdev_read(struct file *file, char __user *buf, size_t nbytes, l 
	}



	if (pos < sizeof(struct usb_device_descriptor)) {

		struct usb_device_descriptor *desc = kmalloc(sizeof(*desc), GFP_KERNEL);

		if (!desc) {

			ret = -ENOMEM;

			goto err;

		}

		memcpy(desc, &dev->descriptor, sizeof(dev->descriptor));

		le16_to_cpus(&desc->bcdUSB);

		le16_to_cpus(&desc->idVendor);

		le16_to_cpus(&desc->idProduct);

		le16_to_cpus(&desc->bcdDevice);

		struct usb_device_descriptor temp_desc ; /* 18 bytes - fits on the stack */



		memcpy(&temp_desc, &dev->descriptor, sizeof(dev->descriptor));

		le16_to_cpus(&temp_desc->bcdUSB);

		le16_to_cpus(&temp_desc->idVendor);

		le16_to_cpus(&temp_desc->idProduct);

		le16_to_cpus(&temp_desc->bcdDevice);



		len = sizeof(struct usb_device_descriptor) - pos;

		if (len > nbytes)

			len = nbytes;

		if (copy_to_user(buf, ((char *)desc) + pos, len)) {

			kfree(desc);

		if (copy_to_user(buf, ((char *)&temp_desc) + pos, len)) {

			ret = -EFAULT;

			goto err;

		}

		kfree(desc);



		*ppos += len;

		buf += len;